Applications in Geotechnical Situations

 

Influences of Plate Tectonics on Geotechnical thinking have been extensive. Implications and consequences of a process, which is ongoing and developmental are greatly pervasive.

Active faulting and seismic activity have come to be recognized as the ordinary state of many geologic situations. Even a perception of style appears possible. The aftermath of the Northridge Earthquake has been influential in focusing dramatically on the need to flesh out tectonic schemes. But, the process appears open-ended, and two more elements have been added recently and provisionally to the scheme -- the Puente Hills Fault and an unnamed fault in coastal Orange County (both blind thrusts).

The situation shown below may be a good illustration of the impact of Plate Tectonic circumstances on concepts of ground stability viz civil structures.

The San Luis Dam and Reservoir in Merced County was completed in the early 1960's, before development and acceptance of the ideas of Plate Tectonics. The recency of the Ortigalita activity had not yet been identified. But, by 1975, the southern part of the Ortigalita fault was recognized as active. And, by 1982, both parts (northern and southern) were considered active. Subsequently, Alquist Priolo zones were drawn into the reservoir. In 1991, a seismic source was identified farther to the east along the supposed boundary of the Coast Range and Sierra blocks. Finally, in 1995, the new California Fault Map shows surface traces of the young San Joaquin and O'Neill fault systems in eastern portions of the San Luis Dam area.

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